Competitor intrusions and mate-search tactics in a territorial marine fish

Recent theoretical studies have drawn attention to the importance of unders tanding the costs females experience during mate choice and mating and how females resolve the trade-offs presented by such costs. In garibaldi damsel fish (Hypsypops rubicundus) females defend permanent feeding and shelter te rritories and must leave their territories to search for and spawn with nes ting males. Both mate searching and spanning occur in bouts, separated by r eturns to the territory. I used focal female observations to test predictio ns of the hypothesis that such behavior is a means of minimizing the amount of food lost to competitors that enter the female's territory while she is searching for or spawning with males. Consistent with this hypothesis, the re was a strong likelihood that the number of intruders entering the territ ory would increase linearly, and hence their total impact exponentially, wi th time away. In addition, the average duration of searching bouts and the duration of a spawning bout were significantly inversely related to a measu re of territorial intruder pressure. Most intruders were heterospecific foo d competitors; incidence of intrusion by conspecifics was rare, and intrudi ng conspecifics did not contest the owner upon her return. In addition, the time females spent in their territories before beginning another bout of s earching was not positively related to the duration of the previous bout. T hus, there is no support for the alternative hypotheses that returning to t he territory is a means of preventing takeover of the territory by conspeci fics or is the result of fatigue.